The Nuclear Safety Commission has allowed the restart of the Hanul Unit 4, which was shut down for a regular inspection.
The Nuclear Safety Commission noted on the 31st that it allowed the criticality of Hanul Unit 4, which began a regular inspection on Oct. 18. Criticality refers to the state where the number of neutrons produced from a nuclear fission reaction equals the number of neutrons lost, thereby achieving a balance. This indicates that the nuclear power plant can operate normally.
The Nuclear Safety Commission explained, "In this regular inspection, out of a total of 91 items, 81 items that needed to be inspected before criticality were examined, confirming that the reactor's criticality can be safely achieved."
During the regular inspection, the suitability of the installation of the reactor head for Hanul Unit 4 was confirmed. The reactor head is the structure installed at the top of the reactor pressure vessel. It has an external control rod drive mechanism that controls the rate of nuclear fission by inserting or controlling control rods, and internally, a nozzle passes through a measuring instrument that monitors the nuclear fuel process, making it a core component of the nuclear power plant. Additionally, inspections of safety-related devices and the condition of piping, as well as a check of the re-installation of the cooling water intake structure anchor, were confirmed to meet standards.
Based on the inspection results so far, the Nuclear Safety Commission has allowed the criticality of Hanul Unit 4 and will conduct final safety verification through the remaining 10 inspection items.